Workers will recognize that various techniques are known for confronting magnetic recording media with a magnetic recording transducer face. For instance, according to one technique, the transducer face is brought into contact with the passing medium. According to another technique ("non-contact" recording) the transducer face is virtually "flown" above the medium and kept out of contact therewith as a guard against damage to the medium, to the face or to both. Generally speaking, workers prefer such "out-of-contact" techniques where feasible. This invention concerns an improvement in "non-contact recording" and an associated novel configuring of the transducer face.
Magnetic memory storage units are a significant item of peripheral equipment in today's computers. In the typical unit data is stored on one or several magnetic disk drives. Such a drive will be recognized as characterized by one or more rotating magnetic recording surfaces on which data may be written, and read back, by a magnetic transducer mounted in a recording head. Such heads are "flown" in close proximity above a recording surface. Great care is taken that this flying head never "crashes" against the disk since catastrophic damage to both can result. Yet, to maximize recording density and optimize signal/noise, workers know that the "head spacing" (spacing between the head-face, and core there, and the surface of the moving disk) must be kept as small as possible and be held within very tight tolerances.
It is common to establish "head spacing" for a "flying head" by configuring the head-face in the fashion of an "air bearing" while establishing the proper fluid dynamics. The magnetic head surface is, today, mounted on a resilient suspension and urged toward the surface of the moving disk by a head-actuation means, but is prevented from actual disk contact by an intervening cushion of air--called a "Bournoulli film" and established as the air bearing. Once this Bournoulli film is developed, it presents a rather substantial hydrodynamic resistance to reduction of "head-spacing" and significant force must be exerted to push the head closer to the disk. But certain abnormal conditions can disturb this "Bournoulli film" and suddenly remove it as a protective cushion, sending the head crashing into the disk. Thus, workers in the art are very meticulous in developing the proper (aerodynamic) head-face configuration and in positioning the head so as to properly orient it (e.g., re pitch and roll angles) relative to the passing disk such close tolerances that a change of a minute of arc or so can be critical!
Workers know that it is critically important to maintain a predicable constant "head spacing" over a wide range of operating parameters if magnetic recording is to be successful. Head spacing is particularly critical with high density recording--e.g., it can vary the "fringing flux" pattern and affect read/write resolution. Workers also know that there are many factors affecting head spacing; such factors as the speed, configuration "penetration" and radial-position of a head [understand: "head speed" as the relative velocity between medium and transducer and "head penetration" as the penetration of the transducer-stabilizer combination into the plane of the passing record medium, causing the latter to "dimple"]. Other affecting factors are disk characteristics (e.g., flexibility, thickness, etc.) and ambient conditions such as temperature and humidity.
Now, it is preferred here that a transducer be thrust to "penetrate" and "dimple" the flexible medium, and so better assure that head spacing be kept constant. However, such a "dimpling" can cause problems. For instance, it may degrade the desired film (Bournoulli) at the disk periphery and cause "flutter" there to upset the prescribed head spacing. Such problems have, to date, limited the useful recording area adjacent a disk's periphery, as workers well know. The present invention is adapted to help in maintaining constant head spacing by eliminating, or at least alleviating, the mentioned problems and so improving disk-head stability--particularly for "flying heads" adapted to transduce for a pack of floppy disks (rather than one disk). In such cases, there will be no "backing plate" (Bournoulli plate) as is typically used with a "single floppy" [e.g., IBM U.S. Pat. No. 4,074,330 mentions that a problem with such Bournoulli plates is that head spacing decreases as the head moves radially-out on the floppy disk--and tries to solve this problem].
Now, the trend today is to record at ever higher "bit densities" (that is, to record individual data transitions that are closer together). And, as bit densities increase, one must reduce the "head spacing" more and more, as workers well know, (also, signal strength increases as head spacing drops). Thus, the task of configuring a head face to create the proper Bournoulli film becomes ever more critical with today's advanced high-bit-density equipment where head spacing on the order of just a few microinches is not uncommon.
This problem is greatly aggravated when one uses flexible disk media (floppy disks). As workers well know, it is not uncommon for such disks to develop surface undulations approximating several dozen microinches under high speed rotation. It is an object of the present invention to develop a novel head configuration adapted to provide a proper "Bournoulli film" cushion when employed with flexible disks under high speed rotation, especially for transducing at high bit densities.